The invention relates to a fuel injection valve for intermittent fuel injection into the combustion chamber of an internal combustion engine according to the preamble of claim 1. The said injection valve may be used, for example in so-called common rail injection systems for diesel engines.
Fuel injection valves of this type are disclosed by the patent specifications EP 0 262 539, EP 0 603 616 or U.S. Pat. No. 5,685,483. In these known fuel injection valves the opening and closing movement of the injection valve member is controlled by controlling the control chamber pressure in a control chamber above a control piston, which is operatively connected to the injection valve member. At the end of its opening movement the injection valve member is stopped by a mechanical stop.
In EP 0 603 616 the injection valve member is long and made up of multiple parts. The length of the injection valve member is dependent upon the engine design according to the injection system application in a certain type of engine. In this known solution the stop is situated at a distance from the upper end of the injection valve member. This causes an oscillation of the free, upper end of the injection valve member after its opening movement has ceased. This oscillation causes undesirable, imprecise closing movements of the injection valve member at the end of the injection sequence.
The injection valve member is also long in EP 0 262 539. The opening movement of the injection valve member is stopped by a stop surface between the upper end of the control piston and an underside of a piston guide part inside the control chamber. Although this arrangement avoids the above-mentioned oscillation, the detachment of the injection valve member from the stop surface at the beginning of the closing movement is associated with uncontrollable, transient fluctuations, which once again cause imprecise closing.
The object of the present invention is both to prevent the oscillation and to ensure detachment of the injection valve member in a precisely controllable manner, so that the injection sequences can be performed with great reproducibility and accuracy.
According to the invention this object is achieved by the features specified in the defining part of claim 1.